Tannin is a polyphenol compound. Tannin in red wine mainly comes from grape skins and seeds, and bitterness in red wine comes from tannin. Red wine with high tannin content is more suitable for aging.
Tannins in grape stems, seeds and skins are the main reasons for the aging ability of red wine. Tannic acid is an astringent in plants, which is the reason for the gritty texture of red wine. They have no taste or fragrance, but they can be experienced as dry.
The word tannin comes from tanning leather with this compound. This is why drinking wine with high tannin without food makes the tongue a bit like leather.
Extended data:
Drinking wine with protein food can reduce the bitterness of wine.
The interaction between tannin and protein and the precipitation of protein are the keys to understand tannin. When tannins come into contact with protein, they combine and sink to the bottom of any container.
This removes protein and tannins from the wine. Too much protein in wine can lead to blurring. However, due to the existence of tannin during fermentation, most of protein was precipitated.
The biggest influence of this interaction comes from drinking red wine. Take a sip of red wine without eating any food, and your tongue will feel dry. This is because tannins in wine combine with protein in saliva.
It is this precipitation that makes red wine match with high-protein foods such as steak and cheese. Tannins combine with extra protein in our mouth to make wine easier to eat.
References:
Baidu encyclopedia-tannin